From patchwork Mon Jul 12 06:12:24 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 473790 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4BABCC07E9B for ; Mon, 12 Jul 2021 07:30:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 32CCC61413 for ; Mon, 12 Jul 2021 07:30:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245279AbhGLHdg (ORCPT ); Mon, 12 Jul 2021 03:33:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:44518 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343963AbhGLH3G (ORCPT ); Mon, 12 Jul 2021 03:29:06 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id B0CE5613D8; Mon, 12 Jul 2021 07:24:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626074684; bh=/4WK8nKUvEkJpigdG4z2qQ+j88Y6mH6qhSyZT5i4Rt0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wS466X/8CPTqp8oIpmBfl2jx1vlhS582zCwzYj8jtL1Hr1m8oRMcZrXXcGt7U5/TA tXBxRKZk1Jy1n1AaqQ2GQxGc8XrlLIrtCbN1yzJaHcmxttwPkTaCPfcjdVR+anSTQ8 5hopRB6ozQHto8WZnKh6huvtq5KR5Y00CXC6B0Hk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, =?utf-8?q?Pali_Roh=C3=A1r?= , Sasha Levin Subject: [PATCH 5.12 661/700] serial: mvebu-uart: correctly calculate minimal possible baudrate Date: Mon, 12 Jul 2021 08:12:24 +0200 Message-Id: <20210712061046.225539114@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060924.797321836@linuxfoundation.org> References: <20210712060924.797321836@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Pali Rohár [ Upstream commit deeaf963569a0d9d1b08babb771f61bb501a5704 ] For default (x16) scheme which is currently used by mvebu-uart.c driver, maximal divisor of UART base clock is 1023*16. Therefore there is limit for minimal supported baudrate. This change calculate it correctly and prevents setting invalid divisor 0 into hardware registers. Signed-off-by: Pali Rohár Fixes: 68a0db1d7da2 ("serial: mvebu-uart: add function to change baudrate") Link: https://lore.kernel.org/r/20210624224909.6350-4-pali@kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/mvebu-uart.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c index 9638ae6aae79..1e26220c7852 100644 --- a/drivers/tty/serial/mvebu-uart.c +++ b/drivers/tty/serial/mvebu-uart.c @@ -481,7 +481,7 @@ static void mvebu_uart_set_termios(struct uart_port *port, struct ktermios *old) { unsigned long flags; - unsigned int baud; + unsigned int baud, min_baud, max_baud; spin_lock_irqsave(&port->lock, flags); @@ -500,16 +500,21 @@ static void mvebu_uart_set_termios(struct uart_port *port, port->ignore_status_mask |= STAT_RX_RDY(port) | STAT_BRK_ERR; /* + * Maximal divisor is 1023 * 16 when using default (x16) scheme. * Maximum achievable frequency with simple baudrate divisor is 230400. * Since the error per bit frame would be of more than 15%, achieving * higher frequencies would require to implement the fractional divisor * feature. */ - baud = uart_get_baud_rate(port, termios, old, 0, 230400); + min_baud = DIV_ROUND_UP(port->uartclk, 1023 * 16); + max_baud = 230400; + + baud = uart_get_baud_rate(port, termios, old, min_baud, max_baud); if (mvebu_uart_baud_rate_set(port, baud)) { /* No clock available, baudrate cannot be changed */ if (old) - baud = uart_get_baud_rate(port, old, NULL, 0, 230400); + baud = uart_get_baud_rate(port, old, NULL, + min_baud, max_baud); } else { tty_termios_encode_baud_rate(termios, baud, baud); uart_update_timeout(port, termios->c_cflag, baud);